This unit interfaces with another system, via either
   FOSSIL or direct UART, using the ZModem protocol.
   It support error-trapping, direct recovering, line faults and
   afterwards Error-recovering from broken transmission.
   It uses ECO_LIB.TPU for a nice directscreen real-time display.
   A version will be written, undependent from ECO_LIB, where
   a pointer to a display routine can be used for either
   no-, direct or stdio screenwrites.